By 1962, the once robust Sino-Soviet alliance had cracked up, revealing serious conflicts beneath the façade of Communist solidarity. This split was a remarkable development in a Cold War context. It was not the first time that the Soviets had fallen out with their allies: the Yugoslavs were thrown out of the “camp” in 1948; Hungary had tried but failed to leave in 1956; Albania quarreled with Moscow in 1961. But, in spite of their intrinsic importance, these issues were small compared to the red banner of Sino-Soviet unity, the symbol of the power and appeal of socialism worldwide. The demise of the alliance represented the broken promise of Marxism. Ideological unity and conformity were so essential to the Soviet-led socialist world that a quarrel between its two principal protagonists – the Soviet Union and the People’s Republic of China – undermined the legitimacy of the socialist camp as a whole, and of the intellectual notions that underpinned its existence.

So inexplicable did the split appear from a Marxist perspective that both Chinese and Soviet historians in retrospect would blame the debacle on the other side’s betrayal of Marxism. But from a realist perspective, Marxism had nothing to do with the rift: the Soviet Union and China were great powers with divergent national interests. No amount of Communist propaganda could have reconciled these competing interests, so it was not surprising, indeed it had been predictable, that the Soviets and the Chinese would fall out and the alliance would crumble.